KVPY Sample Paper KVPY Stream-SX Model Paper-27

  • question_answer
    If \[f(x)=[x]+[x+1/3]+[x+2/3],\] then ([.] denotes the greatest integer function)-

    A) \[f(x)\] is continuous at x= 1, 10, 15

    B) \[f(x)\] is continuous at \[x=n/3,\] where n is any integer

    C) \[\int\limits_{0}^{2/3}{f(x)dx=1/3}\]

    D) \[\underset{x\to 2/3}{\mathop{\lim }}\,f(x)=2\]

    Correct Answer: C

    Solution :

    \[\int\limits_{0}^{2/3}{f(x)dx}\]
    \[\int\limits_{0}^{2/3}{\left( [x]+\left[ x+\frac{1}{3} \right]+\left[ x+\frac{2}{3} \right] \right)}\,\,dx\]
    \[=\int\limits_{0}^{1/3}{0dx}+\int\limits_{1/3}^{2/3}{dx}=\frac{2}{3}-\frac{1}{3}=\frac{1}{3}\]


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